Factors have the most important role on one's personality

Which factors have the most important role on one's personality and how? Genes or environment?
Is it true that many of criminals and indecent people had a difficult childhood and have grown up in an indecent family? And what's your defenition of a decent and indecent family?

I remember hearing a program on the radio a few years back that involved researchers making a claim that they had isolated a gene or genes that caused violent, sociopathic behavior, but that it was rarely expressed in any person that had not experienced a violent event of some sort in early childhood. I'm sure there has to be something you can find in the journals about this, although I personally don't keep up much on behavioral sciences, and honestly, I doubt anyone else here does either.